This invention relates to a device for processing a waveform in a larynx stroboscope adapted to observe vocal cords and diagnose problems in the vocal cords while making audible sounds.
A larynx stroboscope operates to cause a discharge tube to emit light in synchronization with the vibration of vocal cords making sounds and to apply the light to the vocal cords so that the observer can observe the vocal cords as if they were at rest. In order to precisely observe vocal cords being vibrated, it is necessary to receive the vocal cord vibration with a microphone to precisely detect the fundamental wave component included in the vocal cord vibration signal generated by the microphone. This allows the discharge tube to emit light in synchronization with the fundamental wave component. Stated differently, it is necessary to remove as much as possible of the harmonic wave components which obstruct the synchronous light emission of the discharge tube.
Different vocal cord vibration signals are of course detected from different persons by the microphone. In general, the vocal cord vibration signal includes a number of harmonic waves as well as the fundamental wave component. In a conventional larynx stroboscope, a vocal cord vibration signal detected by the microphone is applied to a filter, and the harmonic wave components of the vocal cord vibration signal are removed as much as possible by manually adjusting the frequency band of the filter. The operation can therefore extract the fundamental wave component of the vocal cord vibration signal, so that the discharge tube emits light in synchronization with the fundamental wave component thus extracted.
In this connection, it is emphasized that different vocal cord vibration frequencies are produced by different persons being examined. In addition, the same vocal cord vibration frequency is not always produced by the same person whenever he makes audible sounds. Accordingly, it is necessary for the operator to selectively adjust the frequency band of the filter whenever the vocal cord vibration frequency is changed. However, since the period of time for which the person to be examined can make continuous sounds is limited, the operator must carry out the selective adjustment of the frequency band of the filter. Thus, the operation of the conventional larynx stroboscope is troublesome and not efficient in terms of available examination time. Accordingly the operator cannot entirely devote himself to the observation and diagnosis of the vocal cords of a person to be examined.